Prior art means for securing bearings and rotating anode X-ray tubes have proven to be less than totally satisfactory. The prior art use of tapped holes containing set screws to locate and secure such bearings has resulted in contamination of the bearings by chips resulting from drilling and tapping set screw holes. Also, pressure from set screws has been found to distort bearing races with undesirable accelerated wear. Finally, the thermal cycling to which such bearing mountings are subjected can result in added wear or misadjustment.